This is a two year supplement application. Funding is requested to restore a core unit that was in place in earlier years of the program project. The objective of the core is to ensure that all human study projects within the program have suitable participants available in sufficient number to fulfill each project's specific aims. It recruits and identifies participants with verified diagnostic and developmental status and level of readiness appropriate for each project study. To achieve this objective, the core provides three major support services. It will be responsible for: (1) human studies matters (i.e., recruiting participants, obtaining informed consent, consultation with families and treatment teams, etc.); (2) participant assessment and preparation (i.e., administering a battery of clinical and behavioral assessments to potential participants, following a thorough review of psycho-educational records, and establishing behavioral baselines required for each experiment); and (3) tracking experimental participation and progress.